Add kClipboardContentSetting feature flag for Async Clipboard.

This will be used to control the visibility of the Clipboard Content Setting (coming in a follow-up cl).

Bug: 677564
Change-Id: I80bfcac5b5312d657046b585d82b2e58bd7e315b
Reviewed-on: https://chromium-review.googlesource.com/758459
Commit-Queue: Gary Kacmarcik <[email protected]>
Reviewed-by: Raymes Khoury <[email protected]>
Cr-Commit-Position: refs/heads/master@{#516177}
diff --git a/chrome/browser/flag_descriptions.h b/chrome/browser/flag_descriptions.h
index b0a406d..2de7626 100644
--- a/chrome/browser/flag_descriptions.h
+++ b/chrome/browser/flag_descriptions.h
@@ -96,6 +96,9 @@
 extern const char kClickToOpenPDFName[];
 extern const char kClickToOpenPDFDescription[];
 
+extern const char kClipboardContentSettingName[];
+extern const char kClipboardContentSettingDescription[];
+
 extern const char kCloudImportName[];
 extern const char kCloudImportDescription[];